1. Field of the Invention
This invention relates to a liquid crystal device that modulates light in accordance with supplied image information, and to a projection display apparatus that uses the liquid crystal device.
2. Description of the Related Art
Liquid crystal apparatuses (liquid crystal panels) that modulate light in accordance with supplied image information are widely utilized as direct view display apparatuses and as light valves (light modulators) of projection display apparatuses. FIG. 14 is an exploded view showing the general configuration of a conventional liquid crystal device 1000. The liquid crystal device 1000 is equipped with a liquid crystal cell 1020, a micro-lens array 1030 and two polarizers 1040 and 1050. The liquid crystal cell 1020 has a transparent substrate 1021, an opposed (transparent) substrate 1025 and a liquid crystal layer 1027 set between the transparent substrate 1021 and the opposed substrate 1025. A thin-film transistor 1022 and pixel electrode 1023 are provided on the transparent substrate 1021 for each pixel. A common electrode 1024 is provided on the opposed substrate 1025. A light shield layer 1026 is provided between the opposed substrate 1025 and the common electrode 1024. The light shield layer 1026 has a corresponding opening 1026W for each pixel electrode 1023.
The micro-lens array 1030 is provided on the opposite side of the opposed substrate 1025 to the liquid crystal layer 1027. The micro-lens array 1030 is constituted of a plurality of concentrically shaped micro-lenses 1030M. As shown by FIG. 15, the micro-lenses 1030M are arranged so that the optical axis of each of the micro-lenses 1030M is substantially in alignment with the center axis of the corresponding opening 1026W.
The first polarizer 1040 is provided on the opposite side of the micro-lens array 1030 to the opposed substrate 1025, and the second polarizer 1050 is provided on the opposite side of the liquid crystal cell 1020 to the liquid crystal layer 1027.
In this liquid crystal device 1000, light enters the liquid crystal layer 1027 via the opposed substrate 1025 and exits via the transparent substrate 1021 (the exit surface being the display surface).
The passage of incident light through the liquid crystal device 1000 is illustrated by FIG. 15. The incident light is split into a plurality of beams and is converged by its passage through each of the micro-lenses 1030M of the micro-lens array 1030, and then enters the opening 1026W of the corresponding pixel, from which it passes through the common electrode 1024 and pixel electrode 1023 and exits from the display surface. The light is caused to form an image on the display surface by using the application of a voltage (determined by the image information) between the common electrode 1024 and each pixel electrode 1023 to control (modulate) the light transmissivity of each pixel. In a projection display apparatus that uses this type of liquid crystal device, the image displayed on the liquid crystal device is projected by an optical projection system (such as a projection lens) to be displayed on a screen.
A characteristic of a liquid crystal device is that it changes the contrast of the image displayed on the display surface in the direction in which the image is viewed. Here, the direction in which the image is viewed is termed the viewing angle or viewing angle direction, and is expressed as the angle from the normal of the display surface and the plane angle. Each type of liquid crystal device also has a viewing angle direction (hereinafter referred to as "clear viewing direction") at which contrast is at a maximum (hereinafter referred to as "optimum contrast"). The arrow in FIG. 15 indicates the clear viewing direction VD of the liquid crystal device 1000. Thus, the contrast of the viewed image is best when the light from the display surface of the liquid crystal device exits in a direction that is substantially parallel to the clear viewing direction VD, and when the light exits in a direction that is not parallel to the clear viewing direction VD the contrast is degraded by an amount that is dependent on the direction of the light and increases with the increase in the angle by which the light departs from being parallel with the clear viewing direction VD.
For illumination liquid crystal devices generally employ divergent or substantially parallel light, and light emitted by the display surface includes light with the various directional components. Although it is termed substantially parallel light, the fact is that it includes quite a high proportion of non-parallel components. Therefore, since the contrast of a liquid crystal device is determined by light thus comprised of these various directional components, the contrast of the liquid crystal device is degraded compared to the optimum contrast in the clear viewing direction.
In order for a viewer to obtain a good understanding of images displayed on a liquid crystal device, it is preferable to have good image contrast, a large brightness differential between light display (white screen display) and dark display (black screen display). That is, it is preferable for there to be a large difference between light transmissivity during light display and light transmissivity during dark display. However, the problem with conventional liquid crystal devices is that, as described, owing to the fact that the light consists of various directional components images can be viewed only at a contrast that is degraded compared to the optimum contrast.